Today's workhorse in deep reactive ion etching (DRIE) of high aspect ratio features in silicon is the so-called Bosch process described inter alia in U.S. Pat. No. 5,498,312. This process is the most popular choice of technology in silicon micromachining and serves the huge emerging markets of
1) Through-Silicon Vias (TSVs) for 3D stacking of wafers and dies, and
2) Micro-Electromechanical Systems (MEMS, i.e. sensors and actuators), as well as more mature markets in
3) DRAM trench etching, and Shallow Trench Isolation etching.
The Bosch process is also referred to as Deep Reactive Ion Etching, which is essentially a process of subsequently etching and passivation. Originally, the Bosch process is based on alternating cycles of Si-etching with SF6 or NF3 in Ar to form gaseous SiFx etch products, and passivation with CHF3 or CF4 in Ar to form a protecting fluorocarbon polymer deposit on the sidewalls and bottom of the feature. Time scales of etch and passivation cycles are typically with cycles of several (e.g.) 3-5 seconds.